Local immunoglobulin A in normal and neoplastic breast tissues.

Local IgA levels in 36 normal, 92 nonmalignant atypical, and 47 malignant human breast tissue specimens were analyzed by three methods: direct immunofluorescence, modified radioimmunoassay for IgA in cryostat sections, and the Immuno-Fluor (Bio-Rad Laboratories, Richmond, Calif.) assay for the cell surface IgA in tissue eluates. The proportion of epithelium in each sample was estimated microscopically. For malignant specimens the proportion of epithelial cells was significantly higher than that for nonmalignant specimens. The immunofluorescence test showed no qualitative difference in epithelial IgA content between normal and nonmalignant atypical tissues, but the frequency of positive specimens was markedly lower in malignant tissues. The modified radioimmunoassay and the Immuno-Fluor assay indicated little or no difference in IgA concentration per tissue weight among normal, nonmalignant atypical, and malignant breast tissues. However, when the data were corrected for proportion of glandular epithelium, nonmalignant atypical tissues had less IgA per cell than normal tissues, and malignant mammary carcinomas had significantly less IgA per cell than both normal and nonmalignant atypical tissues.